Possible Clues:

• Intrude, as menu inside has cold fish
• Intrude on somebody's territory or time
• Old chancer used to go a bit too far
• Gradually intrude (upon another's space)
• Cross the line for some tench (fish)
• Go too far in foreign carriage, crossing river
• Advance gradually (beyond expected limits)
• Intrude into another's space
• Intrude (gradually)
• Intrude on someone's property or time